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#include <search.h>ENTRY hsearch (ENTRY item, ACTION action);
int hcreate (size_t nel);
void hdestroy (void);
hcreate allocates sufficient space for the table, and must be called before hsearch is used. nel is an estimate of the maximum number of entries that the table will contain. This number may be adjusted upward by the algorithm in order to obtain certain mathematically favorable circumstances.
hdestroy destroys the search table, and may be followed by another call to hcreate.
#include <stdio.h>
#include <search.h>
#include <string.h>
#include <stdlib.h>
struct info { / this is the info stored in table /
int age, room; / other than the key /
};
#define NUM_EMPL 5000 / # of elements in search table /
main( )
{
/ space to store strings /
char string_space[NUM_EMPL20];
/ space to store employee info /
struct info info_space[NUM_EMPL];
/ next avail space in string_space /
char str_ptr = string_space;
/ next avail space in info_space /
struct info info_ptr = info_space;
ENTRY item, found_item;
/ name to look for in table /
char name_to_find[30];
int i = 0;
/ create table /
(void) hcreate(NUM_EMPL);
while (scanf("%s%d%d", str_ptr, &info_ptr>age,
&info_ptr>room) != EOF && i++ < NUM_EMPL) {
/ put info in structure, and structure in item /
item.key = str_ptr;
item.data = (void )info_ptr;
str_ptr += strlen(str_ptr) + 1;
info_ptr++;
/ put item into table /
(void) hsearch(item, ENTER);
}
/ access table /
item.key = name_to_find;
while (scanf("%s", item.key) != EOF) {
if ((found_item = hsearch(item, FIND)) != NULL) {
/ if item is in the table /
(void)printf("found %s, age = %d, room = %d\n",
found_item>key,
((struct info )found_item>data)>age,
((struct info )found_item>data)>room);
} else {
(void)printf("no such employee %s\n",
name_to_find)
}
}
return 0;
}
Only one hash search table may be active at any given time.